1. Field of the Invention
The present invention relates to a busbar conductor that forms internal circuits of an electric junction box used for connection of automotive electrical instrumentation circuits.
2. Description of the Prior Art
FIG. 4 shows one example of a conventional electric junction box. A case 3, made up of an upper case 1 and a lower case 2, contains a stack of busbar conductors 6, each of which consists of a plurality of busbars 4 and insulating substrate 5. Each busbar has upward or downward projecting tabs 7, which are introduced as connector terminals into connector insertion portions 8, fuse connectors 9 and the like provided to the upper case 1 (or the lower case 2).
A group of busbars 4 are conventionally formed from strips punched out to have desired patterns from the same material (conductive metallic plates of the same thickness, conductivity and material).
The width of each busbar in each layer is determined from a required cross sectional area calculated from the magnitude of current carried and the material's conductivity. The thickness of each busbar is determined by the plate thickness needed for providing the tab 7 with a required strength. The minimum width of each busbar is dictated by the conditions of the material punching process.
Since the number of busbars laid on one insulating substrate 5 is limited by the number of circuits required of an electric junction box and positions where the tabs 7 rise, there is an enough busbar accommodating space on the substrate. Because of this extra space, conventional busbars are often punched from the same material to have a width larger than the minimum busbar width.